The present invention relates to synchronizing devices, especially a synchronizing device for change-speed gears for use with motor vehicles and the like. The type of synchronizing device with which the invention is related includes a gearshift sleeve which is axially guidably carried on a gear-tooth system on a gearshift sleeve carrier such that the gearshift sleeve can be moved into and out of driving connection with a gear-tooth system of a clutch body on a gear to be engaged. See U.S. Pat. No. 3,504,775 for a showing of a prior art synchronizing device of the general type with which the present invention is concerned.
Prior art synchronizing devices of this type have experienced disadvantages "gear hopping" or inadvertent release of the gearshift sleeve from the engaged position with a gear. Investigations of this phenomena of "gear hopping" have revealed that it is caused primarily because of the elastic support of the connection of the transmission, including the synchronizing device, to the vehicle body. Because of this inherent elastic support, movements of the arrangement in a longitudinal direction, combined with thrust and torsional oscillations about the transverse axis, at times stimulate the system shift clutch, shift rod, shift lever and shift button into oscillations so that the oscillating shifting system may overcome the locking force in the gear system, with the consequent "gear hopping" or inadvertent momentary release of the gearshift sleeve from the clutch body of the engaged gear. It has been contemplated to provide means for ramming the shift gearing towards the rear in order to overcome this "gear hopping". While such an arrangement can in fact prevent "gear hopping", the relatively high manufacturing costs of such arrangements has proven to be especially disadvantageous.
A principal object of the invention is to provide a synchronizing device through which this "gear hopping" is positively avoided, and which synchronizing device can be manufactured at low cost.
According to the present invention, the gear-tooth system of the gearshift sleeve carrier and the gear-tooth system of the gearshift sleeve are geometrically configured so as to provide a biasing effect toward the engaged position of the gearshift sleeve, when it has been moved to such engaged position. In preferred embodiments, the gear-tooth system of the gearshift sleeve and sleeve carrier are provided with respective unequal angles of engagement at the interface thereof when the sleeve is in the gear engaged position. Additionally, according to preferred embodiments, the sleeve carrier is provided at this interface with a prescribed chamfer. By this means, inadvertent release of the sleeve or "gear hopping" is prevented with a device which is of low cost to manufacture and which can be utilized with many different types of synchronizing devices. The arrangement of the present invention positively avoids "gear hopping" even with a very elastic aggregate support of the shifting mechanism of a vehicle body.
In particularly preferred embodiments of the invention, the chamfer has an angle of 15.degree. to 35.degree. in relation to the axis of the gearshift sleeve carrier and extends over approximately one-fourth of the width of the gearshift sleeve carrier. In particularly preferred embodiments, the engagement angle .alpha..sub.1 of the gearshift sleeve is larger than the engagement angle .alpha..sub.2 of the gearshift sleeve carrier. In particularly preferred embodiments, the angle of engagement .alpha..sub.1 of the gearshift sleeve is approximately 20 .degree. and the engagement angle .alpha..sub.2 of the gearshift sleeve carrier is approximately 15.degree..